The present invention concerns a power electronic component.
Power electronic components, which are used in particular to construct inverters for rail traction, usually comprise a substrate made of copper, for example. Composite conductor-insulator-conductor structures which have a heat transfer and electrical insulation function are attached to the substrate. They are in the form of a direct bonded copper (DBC) copper-ceramic-copper stack. These composite structures can also be in the form of insulated metal substrates (IMS) which comprise an aluminum or copper bottom layer, an epoxy intermediate layer and a copper top layer which may be formed in several parts.
A plurality of power semiconductor circuits are disposed on each composite structure, for example insulated gate bipolar transistors (IGBT) or diodes. One side of the semiconductor circuits is covered with connecting terminals and the circuits are fixed to the free metal layer of the composite structure on the side with no terminals. The circuits are fixed using tin-lead or tin-lead-silver soft solder, for example.
Aluminum wires typically having a diameter in the range from 380 to 500 microns are then soldered to each connecting terminal. Each of these wires is also soldered to the top metal layer of the composite structure. The assembly of the substrate, the composite structures and the power semiconductor circuits is then placed in a casing filled with silicone gel and covered with an epoxy resin cap to form a power electronic component.
The component is usually placed on a cooling unit which can be a water-cooled plate, an air heat exchanger or a xe2x80x9cheatpipexe2x80x9d evaporator base. This unit is designed to maintain the temperature of the power electronic component below 125xc2x0 C. to maintain its integrity.
The cooling problem is especially critical in the field of power electronic components because the threshold temperature of around 125xc2x0 C. determines the current rating of the component.
In particular, to increase the nominal current capacity of such components it is necessary to increase the quantity of semiconductor material used, which obviously increases the unit cost.
The object of the invention is therefore to improve the cooling of power electronic components in order either to increase the current rating for a given volume and therefore unit price or to reduce the volume and therefore the unit price for a given nominal current.
The invention proposes in particular to provide a power electronic component whose overall structure is different from that of prior art components, and thereby to improve cooling.
To this end, the invention consists in a power electronic component comprising a first heat transfer and electrical insulation composite structure supporting at least one power semiconductor circuit whose side opposite said first composite structure has connecting terminals, said first composite structure including respective conductive or semiconductor layers adjacent and opposite said semiconductor circuit, wherein said connecting terminals are attached on the side opposite said first composite structure to a plane array of mutually insulated conductive members, said array being integrated into at least a second heat transfer and electrical insulation composite structure which includes a conductive or semiconductor layer opposite said semiconductor circuit, and wherein the opposite layer of at least the first composite structure or the second composite structure comprises flow means for a heat transfer fluid.
According to other features of the invention:
the layer opposite the semiconductor circuit is made of a semiconductor material, in particular of silicon;
the semiconductor layer opposite the semiconductor circuit comprises first and second wafers assembled together, at least one of the wafers having grooves, and the heat transfer fluid flow means comprise through passages in said layer opposite the semiconductor circuit, the passages being formed by co-operation of shapes between the wafers;
the plates have respective series of grooves and the passages are formed by co-operation of shapes between said facing grooves on respective opposite sides of the junction plane of the two wafers;
the passages have a hexagonal cross-section;
the layer opposite the semiconductor circuit is made of a metallic material;
the heat transfer fluid flow means open onto the distal face of the metallic layer opposite the power semiconductor circuit;
the flow means comprise at least one passage extending over at least a portion of at least one dimension of the metallic layer opposite the semiconductor circuit;
the terminals are attached to the plane array of the second composite structure by soldering at least one tin-lead-silver boss;
the terminals are separated from the or each boss by a coating adhering to the or each boss, in particular a titanium-nickel-gold deposit.